Baiting the cross-face nerve graft with temporary hypoglossal hookup

BACKGROUND: Cross-face nerve grafting yields inconsistent neural regeneration, and methods that promote more robust axonal traversing of the graft would expand the indications for this procedure. OBJECTIVE: To test the hypothesis that hooking a cross-face nerve graft distally to a source of denervated muscle, rather than leaving it in the subcutaneous space, would positively affect neural ingrowth across the graft, based on elaboration of neurotrophins from the musculature. METHODS: Twenty-four rats underwent cross-face nerve grafting in which the right facial nerve buccal branch was transected and coapted to the graft. The graft was placed across the neck and into the left side of the face. The distal end of the graft was placed either in the left subcutaneous space, coapted to the marginal mandibular branch of the left facial nerve, or coapted to the distal stump of the transected left hypoglossal nerve. Eight control animals underwent right buccal branch transection and placement of a cross-face nerve graft without any proximal and distal hookup. After 12 weeks, all experimental groups underwent hookup of the distal nerve graft to the left facial nerve buccal branch. Vibrissal function was assessed during the ensuing 12 weeks, and then the graft was harvested for histomorphometric analysis. RESULTS: After 12 weeks, there was a significant difference in axon counts between the group coapted distally to the tongue (hypoglossal hookup) and that coapted to the facial musculature (marginal hookup). Twelve weeks later, after distal cross-face nerve graft hookup, this difference was not statistically significant, although the hypoglossally baited group demonstrated statistically significantly greater fiber maturity. Recovery of vibrissal movement did not differ among treatment groups. CONCLUSION: Baiting the cross-face nerve graft via temporary hookup to the distal hypoglossal nerve and tongue musculature appears to improve nerve ingrowth through a nerve graft across the face, although a corresponding improvement in facial muscle function was not observed.     

Trajectory of the hypoglossal nerve in the hypoglossal canal: significance for the transcondylar approach

A microanatomical study of the hypoglossal canal and its surrounding area was carried out using dry skulls and cadaveric heads to determine the course of the hypoglossal nerve in the hypoglossal canal, especially the significance for the transcondylar approach. The hypoglossal nerve enters the superomedial part of the hypoglossal canal as two bundles, which then change course abruptly to an anterosuperior direction, and unite as one trunk before exiting the canal. The hypoglossal nerve has an oblique course in the canal rather than being located in the center, and exits through the inferolateral part of the canal. A venous plexus surrounds the entire length of the nerve bundles in the canal. The present results suggest that during drilling the occipital condyle toward the hypoglossal canal from behind, the surgeon does not need to be overly concerned even if some bleeding occurs from the posterolateral edge of the hypoglossal canal.     

Efficacy of the "baby-sitter" procedure after prolonged denervation

This study was undertaken to evaluate whether 40 percent of the hypoglossal nerve, which showed optimal efficacy in restoring orbicularis oculi muscle (OOM) function after different percentages of partial neurectomy in a previous study would be effective after prolonged denervation time. Twenty Sprague-Dawley rats were divided into four groups. In first-stage surgery the left facial nerve of all animals was transected at the level of the stylomastoid foramen and main zygomatic branch. Group A (controls) consisted of animals with only left facial nerves transected (no repair). In Groups B, C, and D the facial nerve was transected and the facial musculature was denervated for a period of 4, 8, and 12 weeks respectively. During a second-stage procedure, a 40 percent neurectomy was performed on the hypoglossal nerve. Subsequently, a nerve transfer was performed by coaptations of a saphenous nerve graft to the neurectomized hypoglossal nerve and the main zygomatic branch of the facial nerve that innervated the OOM. Behavioral analysis of blink reflex, electrophysiology, and axon and motor end-plate counts in Groups B, C, and D showed superior results compared to Group A. There was no statistically significant difference observed among Groups B, C, and D (p > 0.05). Despite the diminished number of axons in the zygomatic branch and motor end-plates in the orbicularis oculi muscle after 12 weeks of denervation, there was still sufficient muscle target recovery to effect some eye closure in all groups except the controls. This study demonstrated in this model that the 40 percent partial neurectomy of the XII to VII component of the "baby-sitter" procedure was effective even after prolonged denervation.     

Isolated bilateral paralysis of the hypoglossal and recurrent laryngeal nerves (Bilateral Tapia's syndrome) after transoral intubation for general anesthesia

Tapia's syndrome is due to extracranial involvement of the hypoglossal nerve and the recurrent laryngeal branch of the vagal nerve. The injury of these nerves is a rare complication of anesthetic airway management. We present a patient with a postoperative bilateral hypoglossal and recurrent laryngeal nerves palsy after uncomplicated orotracheal intubation. Corticosteroid therapy was started after diagnosis. Forty-eight hours later, the movements of the vocal cords started to recover and full recovery was achieved by the fourth day. Within 3 days, tongue mobility was gradually improved and the patient's symptoms resolved completely by 4 weeks.     

"Triple cross" of the hypoglossal nerve and its microsurgical impact to entrapment disorders.

OBJECTIVE: Cadaveric dissections were performed to review the intracranial and extracranial course of the hypoglossal nerve. The neurological significance of a newly defined "triple cross" of the hypoglossal nerve is discussed. MATERIALS AND METHODS: 10 cadaveric heads (left and right; 20 sides) were dissected using microsurgical techniques. RESULTS: In the cisternal segment of hypoglossal nerve, the diameter of the rostral trunk amounted to 155-680 microm (mean 435 microm), and the caudal trunk to 210-820 microm (mean 482 microm). The roots formed three trunks in 20% of the hypoglossal nerves and two trunks in the rest. As a first cross, the anterior medullary segment of the vertebral artery crossed the hypoglossal nerve roots in 14 of 20 sides (70%). As a rare variation, the vertebral artery extended medial to the nerve (25%) or between its roots (5%). The second cross was found between the descendens hypoglossus and the occipital artery (75%), sternocleidomastoid artery and vein complex (15%) and external carotid artery (10%). The third cross was shown in the submandibular triangle between the lingual hypoglossus and its drainage vein; vena committans nervus hypoglossus. CONCLUSION: Throughout its way, the hypoglossal nerve passes over vascular structures in three crossing points which may serve as a probable cause of hypoglossal nerve entrapment disorders.     

Neuroapraxia del nervio hipogloso tras hemiartroplastia de hombro

We report a case of hypoglossal nerve damage after shoulder hemiarthroplasty with the patient in «beach chair» position, performed with general anesthesia with orotracheal intubation, and without complications. An ultrasound-guided interscalene block was previously performed in an alert patient. After the intervention, the patient showed clinical symptomatology compatible with paralysis of the right hypoglossal nerve that completely disappeared after 4 weeks. Mechanisms such as hyperextension of the neck during intubation, endotracheal tube cuff pressure, excessive hyperextension, or head lateralization during surgery have been described as causes of this neurological damage. We discuss the causes, the associated factors and suggest preventive measures.     

Endoscope-assisted microsurgical resection of an intraneural ganglion cyst of the hypoglossal nerve

An unusual case of an intraneural ganglion cyst of the hypoglossal nerve is presented. Only one case of this rare clinical entity has been reported previously. A 51-year-old woman presented with a 6-month history of left-sided hypoglossal nerve palsy. Magnetic resonance imaging revealed a cystic lesion related to the hypoglossal canal. There was no enhancement of the lesion after administration of Gd. A high-resolution computerized tomography scan of the skull base demonstrated an enlargement of the hypoglossal canal. To access the lesion, a far-lateral endoscope-assisted microsurgical approach was used. An intraneural ganglion lesion invading the hypoglossal nerve was found and resected. A histopathological examination confirmed that the lesion was an intraneural ganglion cyst. The occurrence of an intraneural ganglion cyst at the hypoglossal nerve is very rare. This case exemplifies an atypical location of a synovial cyst with cranial nerve involvement.     

A case of intracranial hypoglossal neurinoma without hypoglossal nerve palsy: operative view of the preserved rostral trunk.

Hypoglossal neurinomas usually manifest with hemiatrophy and weakness of the tongue. A rare case of intracranial hypoglossal neurinoma without preoperative hypoglossal nerve dysfunction and its operative view are presented. A 36-year-old female who presented with headaches and vertigo was admitted to our hospital. The neurological examination revealed bilateral papilledema and mild truncal ataxia, although weakness and atrophy of the tongue were not observed. Magnetic resonance and computed tomography images demonstrated a large foramen magnum tumor without enlargement of the hypoglossal canal. Total removal of the tumor was performed via a lateral suboccipital craniotomy and C1 partial laminectomy. During the operation, two trunks were observed for the hypoglossal nerve at the entrance of the hypoglossal canal. The tumor arose from the caudal trunk, while the intact rostral trunk entered the hypoglossal canal normally. The tumor only developed intracranially, and since the rostral trunk of the hypoglossal nerve was intact, the patient did not present with hypoglossal nerve palsy preoperatively.     

Detailed anatomy of the intracranial segment of the hypoglossal nerve: neurovascular relationships and landmarks on magnetic resonance imaging sequences

OBJECT: The thin hypoglossal nerve can be very difficult to distinguish on magnetic resonance (MR) images. The authors used a combination of sequences to increase the reliability of MR imaging in its demonstration of the 12th cranial nerve as well as to assess the course of the nerve, display its relationships to adjacent vessels, and provide landmarks for evaluating the nerve in daily practice. METHODS: The study group consisted of 34 volunteers (68 nerves) in whom a three-dimensional (3D) Fourier-transformation constructive interference in steady-state (CISS) sequence and a 3D T1-weighted contrast-enhanced magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) sequence were applied. Two trained neuroradiologists collaboratively identified the hypoglossal trigone, preolivary sulcus, 12th cranial nerve, posterior inferior cerebellar artery, vertebral artery, 12th nerve root sleeve, and the hypoglossal canal on each side. The 3D CISS sequence successfully demonstrated the hypoglossal trigone (100% of images), 12th nerve root bundles (100% of images), and 12th nerve sleeves (88.2% of images). The canalicular segment was exhibited with the aid of plain 3D CISS sequences in 74% of images and by using contrast-enhanced 3D CISS sequences and contrast-enhanced MPRAGE sequences in 100% of images. The landmarks that proved useful to identify the cisternal segment of the 12th cranial nerve included the hypoglossal trigone, preolivary sulcus, and 12th nerve root sleeve. Neurovascular contact was identified in 61% of root bundles. The roots were distorted in 44% of these contacts. CONCLUSIONS: The contrast-enhanced 3D CISS sequence consistently displayed the cisternal segment as well as the canalicular segments of the hypoglossal nerve and is, therefore, the best sequence to visualize the complete cranial course of this nerve. Landmarks such as the 12th nerve sleeves can assist in the identification of this nerve.     

Dural arteriovenous fistula of the anterior condylar confluence and hypoglossal canal mimicking a jugular foramen tumor

The anterior condylar confluence (ACC) is located on the external orifice of the canal of the hypoglossal nerve and provides multiple connections with the dural venous sinuses of the posterior fossa, internal jugular vein, and the vertebral venous plexus. Dural arteriovenous fistulas (DAVFs) of the ACC and hypoglossal canal (anterior condylar vein) are extremely rare. The authors present a case involving an ACC DAVF and hypoglossal canal that mimicked a hypervascular jugular bulb tumor. This 53-year-old man presented with right hypoglossal nerve palsy. A right pulsatile tinnitus had resolved several months previously. Magnetic resonance imaging demonstrated an enhancing right-sided jugular foramen lesion involving the hypoglossal canal. Cerebral angiography revealed a hypervascular lesion at the jugular bulb, with early venous drainage into the extracranial vertebral venous plexus. This was thought to represent either a glomus jugulare tumor or a DAVF. The patient underwent preoperative transarterial embolization followed by surgical exploration via a far-lateral transcondylar approach. At surgery, a DAVF was identified draining into the ACC and hypoglossal canal. The fistula was surgically obliterated, and this was confirmed on postoperative angiography. The patient's hypoglossal nerve palsy resolved. Dural arteriovenous fistulas of the ACC and hypoglossal canal are rare lesions that can present with isolated hypoglossal nerve palsies. They should be included in the differential diagnosis of hypervascular jugular bulb lesions. The authors review the anatomy of the ACC and discuss the literature on DAVFs involving the hypoglossal canal.     

A case of intracranial hypoglossal neurinoma with no preoperative hypoglossal nerve palsy

A case of intracranial hypoglossal neurinoma without hypoglossal nerve palsy is reported. A 43-year-old housewife was admitted to our hospital with vertigo and left occipital headache. Neurologically, no cranial nerve deficits were present. CT scan and cerebral angiography showed a mass in the lower left posterior fossa. MRI also revealed a well circumscribed extra-axial mass compressing brain stem and cerebellum to the right. Left suboccipital craniotomy was performed and the tumor was removed subtotally. From the operative findings, the 8th to 11th cranial nerves were not related to the tumor, however, the origin of the tumor was not confirmed. The histology showed Antoni A type neurinoma mixed partially with Antoni B type. After the operation, the tongue deviation appeared to the left, but no other cranial nerve deficit was noticed. Post-operative neuroradiological reexaminations defined slight enlargement of the hypoglossal canal. Then, we concluded that the origin of the tumor must have been the hypoglossal nerve. Most intracranial hypoglossal neurinoma grow in the hypoglossal canal followed by enlargement or erosion of the hypoglossal canal. The author thought that this case suggests that this hypoglossal neurinoma originated from a few rootlets of hypoglossal nerve and grew mainly between the medulla and the hypoglossal canal.     

Surgical anatomy for direct hypoglossal-facial nerve side-to-end "anastomosis".

OBJECT: In this study the authors investigated the histomorphometric background and microsurgical anatomy associated with surgically created direct hypoglossal-facial nerve side-to-end communication or nerve "anastomosis." METHODS: Histomorphometric analyses of the facial and hypoglossal nerves were performed using 24 cadaveric specimens and three surgically obtained specimens of severed facial nerve. Both the hypoglossal nerve at the level of the atlas and the facial nerve just distal to the external genu were monofascicular. The number of myelinated axons in the facial nerve (7228 +/- 950) was 73.2% of those in the normal hypoglossal nerve (9778 +/- 1516). Myelinated fibers in injured facial nerves were remarkably decreased in number. The cross-sectioned area of the normal facial nerve (0.948 mm2) accounted for 61.5% of the area of the hypoglossal nerve (1.541 mm2), whereas that of the injured facial nerve (0.66 mm2) was less than 50% of the area of the hypoglossal nerve. Surgical dissection and morphometric measurements were performed using 18 sides of 11 adult cadaver heads. The length of the facial nerve from the pes anserinus to the external genu ranged from 22 to 42 mm (mean 30.5 +/- 4.4 mm). The distance from the pes anserinus to the nearest point on the hypoglossal nerve ranged from 14 to 22 mm (mean 17.3 +/- 2.5 mm). The former was always longer than the latter; the excess ranged from 6 to 20 mm (mean 13.1 +/- 3.4 mm). Surgical anatomy and procedures used to accomplish the nerve connection are described. CONCLUSIONS: The size of a half-cut end of the hypoglossal nerve matches a cut end of the injured facial nerve very well. By using the technique described, a length of facial nerve sufficient to achieve a tensionless communication can consistently be obtained.     

Reanimation of early facial paralysis with hypoglossal/facial end-to-side neurorrhaphy: a new approach

The classic hypoglossal transfer to the facial nerve invariably results in profound functional deficits in speech, mastication, and swallowing, and causes synkinesis and involuntary movements in the facial muscles despite good reanimation. Techniques such as a hypoglossal/facial nerve interpositional jump graft and splitting the hypoglossal nerve cause poor functional results in facial reanimation and mild-to-moderate hemiglossal atrophy, respectively. Direct hypoglossal/facial nerve cross-over through end-to-side coaptation without tension was done in three fresh cadavers and four patients. The patients had facial paralysis for less than 7 months. Complete mobilization of the facial nerve trunk and its main branches beyond the pes anserinus from the stylomastoid foramen, division of the frontal branch, if necessary, and superior elevation of the hypoglossal nerve after dividing the descendens hypoglossi, thyrohyoidal branches, occipital artery, and retromandibular veins were performed. The end of the facial nerve was hooked up through both a quarter of a partial oblique neurotomy and a perineurial window at the side of the hypoglossal nerve. Temporalis muscle transfer to the eyelids and the first stage of cross-facial nerve transfer were performed simultaneously. None of the patients experienced hemiglossal atrophy, synkinesis, and involuntary movements of the facial muscles. Regarding facial reanimation, one patient had excellent, one patient good, and the others fair and poor results after a follow-up of at least 1 year.     

The blood supply of the hypoglossal nerve and its relevance to carotid endarterectomy.

Since the hypoglossal nerve is liable to injury during carotid endarterectomy and similar procedures, its blood supply was examined in microinjection studies of human cadavers. The nerve is supplied by arteries that arise from the ascending pharyngeal artery as it exits from the hypoglossal canal, the occipital artery as the nerve passes under its branch to the sternomastoid muscle, direct branches from the external carotid artery, and branches from the ascending pharyngeal artery just near the bifurcation of the common carotid artery. Within and close to the tongue, the nerve is supplied by branches from the lingual artery. Damage to the vessels supplying the nerve may account for some cases of hypoglossal palsy after carotid endarterectomy. Possible mechanisms are ischaemia, thermal or electrical injury from diathermy current conducted to the nerve, or intraneural haematoma from rupturing one or more of these fine vessels.     

The optimal transarticular c1-2 screw length and the location of the hypoglossal nerve

BACKGROUND: Injury to the hypoglossal nerve is a complication associated with transarticular C1-2 screw placement. This complication can be caused by a misdirected or too long screw. Little is known about the optimal screw length and its relationship to the hypoglossal nerve. METHODS: Twenty cervical spine specimens were used to study the optimal length of the transarticular C1-2 screw. Using the Magerl technique, a 3.0 mm drill bit was inserted into the C2 lateral mass, passing through the C1-2 facet joint and penetrating the upper portion of the ventral cortex of the lateral mass of the atlas. After drilling, the hole length was measured between the dorsal cortex of the C2 inferior articular process and the ventral cortex of the C1 lateral mass. In addition, six sagittal-sectioned cadavers were carefully dissected to observe the location of the hypoglossal nerve in the anterior aspect of the atlantoaxial region. RESULTS: The results of the measurements showed that the mean optimal screw path length for all specimens was 38.1 +/- 2.2 mm with a range of 34-43 mm. There was no significant difference between sexes in the screw path length (p 0.05). The hypoglossal nerve lies vertically in front of the lateral portion of the C1 lateral mass and the C1-2 facet joint. The area where the hypoglossal nerve lies is approximately 2-3 mm lateral to the middle of the anterior aspect of the C1 lateral mass. CONCLUSIONS :This study suggests that the mean optimal transarticular C1-2 screw length may be 38 mm; however, the determination of the accurate optimal C1-2 screw length should be made on an individual basis. Risk to the hypoglossal nerve can be eliminated if Magerl's technique is performed exactly.     

Hypoglossal schwannoma—successful reinnervation and functional recovery of the tongue following tumour removal and nerve grafting

Objective  Hypoglossal nerve schwannomas are rare tumours that usually cause ipsilateral hypoglossal palsy. This report describes such lesions in two patients and suggests nerve grafting as part of the treatment regimen. Method  Two patients with intra- and extra-dural hypoglossal schwannomas respectively were treated by direct surgery via a postero-lateral approach to the posterior fossa, hypoglossal canal and carotid sheath. Following tumour removal, sural nerve grafting was used to reconstruct the nerves. Unexpectedly, muscle bulk and motor function returned within 6 months in both patients. Conclusion  Nerve grafting was highly successful in achieving functional recovery following surgery for hypoglossal nerve schwannomas.     

Facial nerve reconstruction using a split hypoglossal nerve with preservation of tongue function

A prospective study conducted on 13 patients suffering from complete facial nerve injury (for 4 months up to 2 years) aimed to show that using the split hypoglossal nerve allows for reconstruction of the facial nerve with preservation of tongue function. The hypoglossal nerve was split longitudinally. For each half, a split of the hypoglossal nerve's response was measured intraoperatively by recording the compound muscle action potential of the tongue muscle. The half that showed the least response was selected for anastomosis. The facial nerve was transected at the stylomastoid foramen, and its distal part underwent a direct anastomosis with the selected half of the hypoglossal nerve. The six grades of the House-Brackman grading system were used to analyze the results. The average postoperative follow-up period was 3 years. Before surgery, 12 patients in this study were graded VI, with total paralysis, and 1 was graded V. After surgery, 2 of the 13 patients showed mild dysfunction (grade II), 7 patients showed moderate dysfunction (grade III), 3 patients showed moderately severe dysfunction (grade IV), and 1 patient showed a severe dysfunction (grade V). Microsurgical facial nerve reconstruction using a split hypoglossal nerve results in functional facial nerve improvement with preservation of tongue function.     

Hypoglossal nerve palsy in nasopharyngeal carcinoma.

BACKGROUND: The aim of the study was to use magnetic resonance (MR) imaging to determine the cause of hypoglossal nerve palsy and the sites of injury in patients with nasopharyngeal carcinoma before radiation therapy and during postradiation therapy follow-up. METHODS: The clinical records and MR studies of 21 patients with hypoglossal nerve palsy were retrospectively studied. These 21 patients belonged to a cohort of 387 patients with nasopharyngeal carcinoma (153 with newly diagnosed disease and 234 on postradiation follow-up) who underwent MR imaging in a 2.5-year period. RESULTS: Four patients had hypoglossal nerve palsy at initial diagnosis and all of them had extensive skull base invasion from tumor extending postero-inferiorly to the level of the foramen magnum. The nerve was invaded in the carotid sheath (3), hypoglossal nerve canal (3), and premedullary cistern (1). In 17 patients developing hypoglossal nerve palsy after radiotherapy, only two (12%) had evidence of tumor recurrence. Radiation-induced neuropathy was the probable cause in 14 patients and 1 case was judged indeterminate. MR evidence of fibrosis was demonstrable along the course the nerve in four patients (29%), involving the carotid sheath (4), hypoglossal nerve canal (2), and premedullary cistern (1). No patient had MR evidence of radiation change in the brain stem. Seven patients had a history of a boost dose of radiation to the parapharyngeal region on one or both sides, and nerve palsy occurred on the boosted side in six of them. CONCLUSION: Hypoglossal nerve palsy on presentation was caused by locally advanced nasopharyngeal tumor whereas a palsy arising after radiation therapy was more frequently caused by postradiation damage rather than cancer.     

Cranial nerve injuries associated with carotid endarterectomy. A prospective study

To determine the incidence and nature of cranial nerve damage in connection with carotid artery surgery, 139 patients were studied before and after 162 operations. Nerve damage was detected in association with 19.8% of the operations. The hypoglossal nerve was most commonly affected. The injuries were of benign character and usually resolved within 4 to 6 weeks. Apart from damage to the great auricular nerve, all lesions resolved within 5 months. The incidence of nerve disturbance was greater than that found in a retrospective study from the same hospital. Gentleness of technique is important in carotid artery surgery, in order to avoid nerve damage.     

Reanimation of the paralyzed face by indirect hypoglossal-facial nerve anastomosis

BACKGROUND: The results of indirect hypoglossal facial nerve anastomosis with interposition of a free nerve graft, end-to-end to the periferal facial nerve stump, and end-to-side to the hypoglossal nerve are prospectively evaluated. This technique is supposed to overcome loss of hypoglossal function. METHODS: Tongue function in 39 consecutive patients and facial reanimation in 29 patients who completed 24 months follow-up were assessed. Facial nerve function was judged using the House-Brackmann (HB) grading system. RESULTS: Tongue movements were normal in all operated on patients. Initial facial movements occurred on average 7.5 months postoperatively. The results were graded HB II in 6 (20.9%), HB III in 13 (44.6%), HB IV in 7 (24.1%), HB V in 2 (6.8%) patients, and HB VI in 1 (3.4%) patient. The results were significantly better in young patients and when a short time interval between paralysis and surgery existed. CONCLUSIONS: Indirect hypoglossal-facial anastomosis is the preferred technique in most patients for whom the classical direct hypoglossofacial anastomosis is indicated.